Download Bringing in Irrigation

Irrigating Corn to Adapt to
Climate Change
PIAMDDI Project Meeting, December 13, 2013
Stanford University
(Monika Verma, Noah Diffenbaugh, Tom Hertel)
Climate-Energy-Policy Interaction
What we missed was Adaptation:
• How can policy on bio-fuels affect it? Trade?
1
Recap
What about irrigation as adaptation?
Corn price Standard Deviation quadruples due to doubled SD of US corn yields,
driven by Climate change
2
Irrigation’s Potential Impact
• How irrigation affects yield (model input, US
yield SD) 𝑌𝑅𝑈𝑆,𝑡 = 𝑐 𝑤𝑐 𝑌𝑅𝑐𝑡
• S&R: effect of temperature much different in
East and West, major difference - irrigation
Source: Schlenker and Roberts, PNAS 2009, Fig A10
3
Yield Variability as input
Same functional form
Irrigated and non-irrigated corn production shares in county’s corn production
4
• USDA-NASS data for Nebraska– irrigated and
non-irrigated corn yield/production county
data (1990-2012)
• Construct the same metric for Nebraska
– Yield SD for irrigated corn: 0.12
– Yield SD for non-irrigated corn: 0.34 (~ 3 times)
– Yield SD: 0.15
5
•Question, what our previous graphs would look
like with irrigation.
– Focus on simple case, leave out policy and oil price
scenarios, concentrating on just climate change
+
+ irrigation
– How do we bring in irrigation into our standard
model framework, for comparison with earlier
results?
6
𝑌𝑅𝑈𝑆 =
𝑤𝑐 𝑤𝑐𝑖 𝑌𝑅𝑐𝑖 + 𝑤𝑐𝑛 𝑌𝑅𝑐𝑛
𝑐
=
𝑤𝑐 𝑌𝑅𝑐𝑛
𝑐
𝑌𝑅𝑐𝑖
𝑤𝑐𝑖
+ 𝑤𝑐𝑛
𝑌𝑅𝑐𝑛
• what we had with our no-irrigation story
• Know its present climate SD
• Know that it doubles with climate change
A more generic version, including irrigation
7
Implications
• Case 1: No Irrigation (𝑤𝑖 = 0, 𝑤𝑛 = 1)
𝑌𝑅𝑈𝑆 =
𝑤𝑐 𝑌𝑅𝑐𝑛
𝑐
– Same as NCC work form, with no irrigation
8
• Case 2: Full Irrigation (𝑤𝑖 = 1, 𝑤𝑛 = 0)
𝑌𝑅𝑐𝑖
𝑌𝑅𝑈𝑆 =
𝑤𝑐 𝑌𝑅𝑐𝑛
𝑌𝑅𝑐𝑛
𝑐
Simplifying assumptions in absence of data –
• NE data applies to all counties/states
…
𝑒 ф𝑐𝑖 . 𝑒 𝑃𝑐𝑖
…
𝑌𝑅
𝑐𝑖
• UNL study to approximate 𝑒 ф𝑐𝑛… . 𝑒𝑃𝑐𝑛… = 𝑌𝑅𝑐𝑛
Cassssman 2009)
…
…
𝑒 ф𝑐𝑖
−0.32
𝑒 𝑃𝑐𝑖
… =
and 𝑃𝑐𝑛…
𝑒 ф𝑐𝑛
−0.34
𝑒
𝑌𝑅𝑐𝑖
•
= 0.42 < 1 implies
𝑌𝑅𝑐𝑛
=
(Grassini, Yang,
0.30
0.67
“year on year yield ratios for fully irrigated crop are less than those for
non-irrigated crop, hence pointing to potential of irrigation as adaptation”
• SD with irrigation = 0.42*SD without irrigation
9
• Case 3: Partial irrigation (𝑤𝑖 = 𝑎, 𝑤𝑛 = 1 − 𝑎)
𝑌𝑅𝑐𝑖
𝑌𝑅𝑈𝑆 =
𝑤𝑐 𝑌𝑅𝑐𝑛 1 − 𝑤𝑐𝑖 1 −
𝑌𝑅𝑐𝑛
𝑐
0<(.)<1
0<(.)<1
– SD is decreasing in share of production under
irrigation
𝑌𝑅𝑐𝑖
+ (𝟏 − 𝒂)
𝑌𝑅𝑐𝑛
Rebased
SD (US yield)
Case1: no irrig
1
1.09
23.89
Case3(Base for 2001):
0.14
0.92
1
21.92
Case2: full irrig
0.42
0.46
10.03
𝒂
𝒂
10
Implementation
11
120
100
X: corn yield SD
Y: corn price SD
NCC+14R
80
NCC+100R
60
40
20
0
-40
-30
-20
-10
0
10
20
30
40
-20
-40
-60
120
100
Vertical distance: difference
in price SD coming from
irrigation
80
NCC+14R
60
NCC+100R
40
20
Y: corn price SD
Two points on same vertical line
represent same climate realization
0
-20
-40
12
-60
600
400
350
500
300
400
250
300
200
CC+14R
200
CC+100R
100
CC2+14R
150
CC2+100R
50
100
0
0
-80
-60
-40
-20
-80
0
20
40
60
80
-60
-40
-20
-50
-100
-100
600
400
0
20
40
60
80
350
500
300
400
300
200
100
0
250
CC+14R
CC+100R
200
150
100
CC2+14R
CC2+100R
50
0
-50
-100
-100
13
Price and Yield SD under different
climate and irrigation combinations
200
44
180
14R
100R
160
39
120
100
80
60
Corn Price SD
140
22
20
10
40
4
20
0
NCC
CC
CC2
Climate Scenario
Height of Bar indicates Price SD and number next to bar is the yield SD
14
• Strange result (with irrigation even after climate change we
get less variability than under same irrigation % and no
climate change)
– Other study: one from Swiss corn (Finger et al 2011, ClimChng)
• Bring in more economics: even if irrigation is effective, under
what conditions would it be feasible/viable to use
– One approach would be to take multiple corn price realizations for
future and see if its profitable for farmers to use surface, ground
water to irrigate
– Cost of irrigation, infrastructure.
• Collaborate with actual working water model and see if these
insights hold, magnitude of impact would likely change
15
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